Controlling generated setting on property in NHibernate

Question

I have a case where one of the columns on the database is generated using a trigger because of a specific way we generate this value which I can't change. If I in my mapping in NHibernate sets the property to generated=insert, it works like a charm, where NHibernate inserts the row without the generated property, and afterwards does a select to pull the value from the database.

But I also have cases where I want to be able to set the property explicitly (the trigger is built to only set the column if it's not set). But I can't get NHibernate to allow me to do this. When it's set to generated=insert, it will always ignore the property I set in my object. So I really want to be able to somehow tell NHibernate that when the property is "untouched"/null, act as property is generated, but if set, don't.

Is it possible to configure NHibernate this way somehow?

Answer 1

Documentation for the generated property states (emphasis mine):

Properties marked as generated must additionally be non-insertable and non-updateable. Only Section 5.1.7, “version (optional)”, Section 5.1.8, “timestamp (optional)”, and Section 5.1.9, “property” can be marked as generated.

Is it a property that can be set as nullable in your domain model so on the initial insert nothing goes into it and your trigger still thinks it's untouched?

Answer 2

My domain model allows for null insertion of the value. And my trigger is made to only set the column if null inserted. What I'm trying to achieve is to at runtime decide, wether or not NHibernate should handle it as a generated property.

But from what I can understand, NHibernate does not have this sort of flexibility and somewhat strides against it's configuration structure where it builds a session factory once for multiple uses.

The alternative solution could be to build two session factories, one for each of my scenarios. The first (where property is generated) is normal usage. The second (where property is non-generated) is during upload scenarios where I need to maintain the property value in the code. I'm using FluentNHibernate for the mappings, and since it reflects over my mapping classes, I could set a state during creation of session factories, so when my mapping is being read, I could do an if/else statement based on which session factory is currently being built. This should allow me to achieve both without duplicate configurations, although with two session factories in play instead of one.

I haven't tried it yet, only theory, but it should solve my problem and hopefully others trying to achieve similar.

Answer 3

I don't think you can achieve this through configuration. However, you can simply call ISession.Refresh(myObject) after an insert to force it to go back to the database and refresh the object.